A large-cavity pile foundation wall stability monitoring test device and method

Abstract

The present invention provides a large-cavity pile foundation retaining wall stability monitoring test device and method, which belongs to the technical field of pile foundation construction process monitoring. The device comprises a geotechnical model trough, foundation filler, large-cavity filler, a pile foundation cavity, a steel cage, a box, a pressure measuring unit and a displacement measuring unit. The pile foundation cavity and the box are connected in a geotechnical model trough containing the foundation filler, the large-cavity filler is filled into the box to form a large-cavity retaining wall, and then the steel cage fixedly connected with the pressure measuring unit and the displacement measuring unit is fixedly inserted into the pile foundation cavity, and the steel cage extends into the large-cavity retaining wall, concrete is poured into the pile foundation cavity, the lateral pressure of the concrete on the inner wall of the large-cavity retaining wall is monitored by the pressure measuring unit, and whether the outer wall of the large-cavity retaining wall is damaged is monitored by whether the displacement measuring unit undergoes lateral displacement, thereby simulating the stability monitoring of the large-cavity retaining wall during pile foundation construction.

Description

Technical Field

[0001] The invention belongs to the technical field of pile foundation construction process monitoring, and in particular relates to a large-cavity pile foundation retaining wall stability monitoring test device and method. Background Art

[0002] Large cavities, as a typical complex condition of karst geology, pose many severe challenges to pile foundation construction. Their irregular cavity shape, variable large cavity filling materials, and unstable stratum structure not only pose a serious threat to the stability of the pile foundation, but also greatly affect the bearing capacity and durability of the pile foundation. In severe cases, they may lead to major engineering accidents. The methods commonly used for pile foundation construction of this type of project are advance pre-grouting consolidation, backfilling, and casing follow-up. At present, it is difficult to determine whether the self-stability of the large cavity filling wall in the cave cavity can support the lateral pressure caused by the concrete pouring process and the lateral pressure generated by the mud in the hole, which in turn affects the judgment of the pile body quality and bearing capacity after the pile is completed.

[0003] The Chinese invention patent with publication number "CN111733787B" discloses a "method and system for detecting the effect of cave treatment during bridge pile foundation construction." The invention includes a temperature field change monitoring system and a bridge pile foundation-soil-cave temperature field simulation model system. The temperature data during the bridge pile foundation construction process is obtained through the temperature field change monitoring system, and the concrete volume and various thermal coefficient parameters in the cave area in the bridge pile foundation-soil-cave temperature field simulation model are continuously adjusted. The node temperature simulation data corresponding to the temperature sensor position in the field test is extracted, and the consistency between the field data and the simulation data is observed. The accuracy of the temperature field simulation model is verified using the field monitoring temperature data. The concrete pouring volume in the cave area can be determined based on the simulation model that is consistent with the field monitoring data, thereby obtaining the excess concrete volume in the cave area, thereby judging the treatment effect of the cave treatment technology used on site. However, when detecting the cave, this invention only measures the temperature near the cave through a temperature sensor to verify the accuracy of the temperature field simulation model by monitoring the temperature data. Before the pile foundation construction, the cave needs to be filled with a mixture of stone chips, clay, cement, etc. to form a cave retaining wall. The formed retaining wall is easy to become unstable during the pile foundation construction, thereby causing depression. Therefore, the cave retaining wall needs to be monitored during the pile foundation construction. This invention does not monitor the stability of the cave retaining wall.

[0004] Therefore, the shortcoming is that the invention cannot monitor the stability of the cave retaining wall during the pile foundation construction process. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a large cave pile foundation retaining wall stability monitoring test device and method, which is used to solve the problem that the prior art cannot monitor the stability of the cave retaining wall.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a large-cavity pile foundation retaining wall stability monitoring test device, the test device comprising:

[0007] A geotechnical model trough, a large dissolution cavity filler, a pile foundation cavity and a box body, wherein the geotechnical model trough is filled with the foundation filler, the box body is buried in the foundation filler, the large dissolution cavity filler is filled into the box body to form a large dissolution cavity protective wall, the volume of the large dissolution cavity protective wall is smaller than the volume of the box body, and the pile foundation cavity extends into the large dissolution cavity protective wall after the foundation filler penetrates the box body;

[0008] A steel cage is fixedly inserted into the pile foundation cavity, wherein the axial direction of the steel cage is consistent with the axial direction of the pile foundation cavity;

[0009] A plurality of pressure measuring units, wherein the plurality of pressure measuring units are arranged in a circular array along the axial direction of the steel cage, the pressure measuring units including pressure sensors, the pressure sensors being fixedly connected to the steel cage, the pressure sensors being located within the large dissolution cavity retaining wall, and when concrete is poured within the pile foundation cavity, the pressure sensors monitor the pressure of the concrete within the large dissolution cavity retaining wall to reflect the lateral pressure of the inner wall of the large dissolution cavity retaining wall;

[0010] The displacement measuring unit includes a plurality of displacement measuring components, each of which is fixedly connected to the steel cage. The plurality of displacement measuring components are arranged in a circular array along the axial direction of the steel cage. When the outer wall of the large cavity protective wall is destroyed under the pouring of concrete, the displacement measuring components generate lateral displacement with the flow of concrete to reflect whether the outer wall of the large cavity protective wall is destroyed.

[0011] As an optional solution, the displacement measurement assembly includes a flexible inclinometer tube and an array displacement meter;

[0012] The flexible inclinometer tube is fixed on the steel cage, the axial direction of the flexible inclinometer tube is parallel to the axial direction of the steel cage, and the array displacement meter is fixedly installed in the flexible inclinometer tube;

[0013] When the outer wall of the large cavity protective wall is destroyed by concrete, the array displacement meter generates lateral displacement along the flow direction of the concrete.

[0014] As an optional solution, the flexible inclinometer tube and the array displacement meter are both located inside the steel cage.

[0015] As an optional solution, the portion of the flexible inclinometer tube extending into the pile foundation cavity above the large dissolution cavity retaining wall is the first portion, and the portion of the flexible inclinometer tube extending into the pile foundation cavity within the large dissolution cavity retaining wall is the second portion;

[0016] The first portion is fixedly connected to the steel cage, and the second portion is not fixedly connected to the steel cage.

[0017] As an optional solution, the pressure measuring unit further includes a protective tube and a fixing bracket;

[0018] The pressure sensor is installed in the protective tube, and the pressure measuring surface of the pressure sensor is close to the inner wall of the large dissolution cavity protective wall to measure the lateral pressure of the inner wall of the large dissolution cavity protective wall in the pile foundation;

[0019] One end of the fixing bracket is fixedly mounted on the protection tube, and the other end of the fixing bracket includes a plurality of fixing ends, and the plurality of fixing ends are all fixedly connected to the steel cage.

[0020] As an option, the pressure sensor is located outside the steel cage.

[0021] The present invention also provides a large-cavity pile foundation retaining wall stability monitoring test method, including the large-cavity pile foundation retaining wall stability monitoring test device described above, the test method comprising:

[0022] Preparation steps: prepare a geotechnical model trench filled with foundation filling, bury a box in the foundation filling, and drill a pile foundation cavity in the foundation filling so that the pile foundation cavity passes through the box from top to bottom and communicates with the interior of the box;

[0023] Large cavity backfilling step: put the large cavity filler into the box through the pile foundation cavity, and repeatedly drill the large cavity filler into the box through the drilling rig to form a large cavity protective wall;

[0024] Installation steps: Install the pressure sensor, flexible inclinometer tube and array displacement meter on the steel cage;

[0025] Steps for lowering the steel cage: insert the steel cage into the pile foundation cavity and fix it;

[0026] Pouring step: pouring concrete into the pile foundation cavity;

[0027] Monitoring steps: monitor the lateral pressure of concrete on the inner wall of the large cavity retaining wall through a pressure sensor, and determine whether the large cavity retaining wall is damaged by observing whether the array displacement meter produces lateral displacement.

[0028] As an optional solution, in the installation step, the pressure sensor, the flexible inclinometer tube and the array displacement meter are all arranged in a circular array along the axial direction of the steel cage.

[0029] As an optional solution, in the monitoring step, the pressure sensor measures the change of the lateral pressure of the concrete on the large cavity retaining wall to reflect the stress condition of the inner wall of the large cavity retaining wall.

[0030] As an optional solution, in the monitoring step, when the large cavity protective wall is destroyed by concrete, the array displacement meter generates lateral displacement along the flow direction of the concrete.

[0031] As described above, the large-cavity pile foundation retaining wall stability monitoring test device and method of the present invention have at least the following beneficial effects:

[0032] 1. The present invention can monitor the lateral pressure inside the large cavity protective wall through a pressure sensor, and when the outer wall of the large cavity protective wall is destroyed under the pouring of concrete, the displacement measuring component will produce lateral displacement with the flow of concrete to reflect whether the outer wall of the large cavity protective wall is destroyed, thereby simulating the stability monitoring of the large cavity protective wall by the pressure sensor and the displacement measuring component during pile foundation construction.

[0033] 2. When recording the pressure data monitored by the pressure sensor at each time point collected by the pressure data collector, the present invention correspondingly observes and records the liquid level of concrete in the pile foundation cavity at each time point, thereby deriving the relationship between the pressure data monitored by the pressure sensor at each time point collected by the pressure data collector and the liquid level of concrete in the pile foundation cavity, so as to simulate the amount of concrete loss during the actual construction process, so that the amount of concrete used can be prepared during the actual construction process, and concrete can be replenished in time when the concrete liquid level in the pile foundation cavity drops.

[0034] 3. The present invention determines whether the outer wall of the large cavity protective wall farthest from the array displacement meter where the lateral displacement occurs is damaged based on the data collected by the displacement data collector. Then, the simulation can be repeated multiple times by changing the composition material of the large cavity protective wall or the thickness of the large cavity protective wall, etc., until the outer wall of the large cavity protective wall is not damaged (that is, the array displacement meter does not undergo lateral displacement), thereby simulating the critical value at which the outer wall of the large cavity protective wall is not damaged, so as to be put into use in actual construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Shown is a cross-sectional view of the structure of the present invention;

[0036] Figure 2 Shown is an internal cross-sectional view of the pile foundation cavity and box of the present invention;

[0037] Figure 3 Shown is a schematic structural diagram of the pressure sensor of the present invention;

[0038] Figure 4Shown is a partial schematic diagram of the pressure data collector and displacement data collector of the present invention;

[0039] Figure 5 Shown is a radial cross-sectional view of the steel cage of the present invention;

[0040] Figure 6 Shown is a schematic structural diagram of the protection tube and the fixing structure of the present invention;

[0041] Figure 7 It is a schematic diagram showing the movement of the concrete of the present invention within the pile foundation cavity and the large dissolution cavity retaining wall.

[0042] In the figure: 101, geotechnical model trough; 102, foundation filling; 103, pile foundation cavity; 104, box; 105, steel cage; 106, large cavity retaining wall;

[0043] 201, pressure sensor; 202, pressure data collector; 203, protective tube; 204, fixed bracket; 205, fixed end; 206, pressure measuring surface;

[0044] 301. Flexible inclinometer tube; 302. Array displacement meter; 303. Displacement data collector. DETAILED DESCRIPTION

[0045] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0046] See also Figures 1 to 7 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they have no substantive technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0047] The following embodiments are for illustration only and can be combined with each other, and are not limited to the contents presented in the following single embodiments.

[0048] See also Figure 1 、 Figure 3 and Figure 4The present invention provides a large-cavity pile foundation wall stability monitoring test device, the test device comprising:

[0049] A geotechnical model trough 101, a large cavity filler, a pile foundation cavity 103, and a box 104. The geotechnical model trough 101 is filled with a foundation filler 102. The box 104 is buried in the foundation filler 102. The large cavity filler is filled into the box 104 to form a large cavity retaining wall 106. The volume of the large cavity retaining wall 106 is smaller than that of the box 104. The pile foundation cavity 103 extends into the large cavity retaining wall 106 after the foundation filler 102 penetrates the box 104.

[0050] The volume of the box 104 is the same as or proportional to the volume of the large dissolution cavity during the actual construction process;

[0051] The wall filler forms a large truncated cone-shaped cavity wall 106 in the box body 104;

[0052] A steel cage 105 is fixedly inserted into the pile foundation cavity 103 , wherein the axial direction of the steel cage 105 is consistent with the axial direction of the pile foundation cavity 103 ;

[0053] A plurality of pressure measuring units are arranged in a circular array along the axial direction of the steel cage 105. The pressure measuring units include pressure sensors 201. The pressure sensors 201 are all fixed to the steel cage 105. The pressure sensors 201 are located in the large dissolution cavity retaining wall 106. When concrete is poured in the pile foundation cavity 103, the pressure sensors 201 monitor the pressure of the concrete in the large dissolution cavity retaining wall 106 to reflect the lateral pressure of the inner wall of the large dissolution cavity retaining wall 106.

[0054] The test device further includes a pressure data collector 202, and the pressure data collector 202 is electrically connected to the pressure sensor 201;

[0055] The displacement measuring unit includes a plurality of displacement measuring components, which are all fixed to the steel cage 105. The plurality of displacement measuring components are arranged in a circular array along the axial direction of the steel cage 105. When the outer wall of the large cavity protective wall 106 is destroyed under the pouring of concrete, the displacement measuring components generate lateral displacement with the flow of concrete to reflect whether the outer wall of the large cavity protective wall 106 is destroyed.

[0056] In this embodiment, when a large cavity protective wall 106 is formed in the box body 104 and the steel cage 105 is fixedly inserted into the pile foundation cavity 103, concrete is poured into the pile foundation cavity 103, and then the pressure sensor 201 monitors the lateral pressure of the concrete on the inner wall of the large cavity protective wall 106. The pressure sensor 201 will transmit the pressure data to the pressure data collector 202, and the pressure data collector 202 will process the data and output the result. If the outer wall of the large cavity protective wall 106 is destroyed by concrete, the concrete will flow toward the place where the protective wall filler is not filled in the box body 104, and the displacement measurement component will produce lateral displacement with the flow of concrete. The present invention can monitor the lateral pressure inside the large cavity protective wall 106 through the pressure sensor 201, and transmit it to the pressure data collector 202 for quantitative analysis of the lateral pressure inside the large cavity protective wall 106. When the outer wall of the large cavity protective wall 106 is destroyed under the pouring of concrete, the displacement measuring component will produce lateral displacement with the flow of concrete to reflect whether the outer wall of the large cavity protective wall 106 is destroyed, thereby simulating the stability monitoring of the large cavity protective wall 106 by the pressure sensor 201 and the displacement measuring component during pile foundation construction.

[0057] See also Figure 2 and Figure 4 The displacement measurement assembly includes a flexible inclinometer tube 301 and an array displacement meter 302;

[0058] The flexible inclinometer tube 301 is fixed on the steel cage 105, and the axial direction of the flexible inclinometer tube 301 is parallel to the axial direction of the steel cage 105. The array displacement meter 302 is fixedly installed in the flexible inclinometer tube 301;

[0059] The test device further includes a displacement data collector 303, which is electrically connected to the array displacement meter 302;

[0060] When the outer wall of the large cavity protection wall 106 is destroyed by concrete, the array displacement meter 302 generates lateral displacement along the flow direction of the concrete.

[0061] In this embodiment, when a large cavity protective wall 106 is formed in the box body 104 and the steel cage 105 is fixedly inserted into the pile foundation cavity 103, concrete is poured into the pile foundation cavity 103. If the outer wall of the large cavity protective wall 106 is damaged by the concrete, the concrete will flow toward the unfilled area of ​​the protective wall filler in the box body 104. The array displacement meter 302 will produce lateral displacement as the concrete flows. The array displacement meter 302 will then transmit the displacement data to the displacement data collector 303. The displacement data collector 303 will process the data and output the result. The present invention can monitor whether the outer wall of the large cavity protective wall 106 is damaged by the array displacement meter 302, and transmit the data to the displacement data collector 303 for quantitative analysis of the lateral displacement of the array displacement meter 302 after the outer wall of the large cavity protective wall 106 is damaged.

[0062] See also Figure 4 The flexible inclinometer tube 301 and the array displacement meter 302 are both located inside the steel cage 105 .

[0063] In this embodiment, when the outer wall of one of the large cavity protective walls 106 is destroyed by the poured concrete, the concrete will pass through the outer wall of the destroyed large cavity protective wall 106 and flow toward the place where the protective wall filler is not filled in the box body 104. At this time, the array displacement meter 302 farthest from the destroyed large cavity protective wall 106 will move in the steel cage 105 along the flow direction of the concrete. When determining which array displacement meter 302 is farthest from the destroyed large cavity protective wall 106, the array displacement meter 302 with the largest lateral displacement displayed in the displacement data collector 303 is the array displacement meter 302 farthest from the destroyed large cavity protective wall 106. The present invention installs the flexible inclinometer tube 301 and the array displacement meter 302 in the steel cage 105 so that the flexible inclinometer tube 301 and the array displacement meter 302 can only displace laterally in the steel cage 105. This ensures that during the test, the flexible inclinometer tube 301 and the array displacement meter 302 will not come into contact with the damaged large cavity protective wall 106, thereby causing damage to the flexible inclinometer tube 301 and the array displacement meter 302.

[0064] See also Figure 2 and Figure 4 , the portion of the flexible inclinometer tube 301 extending into the pile foundation cavity 103 located above the large dissolution cavity protective wall 106 is the first portion, and the portion of the flexible inclinometer tube 301 extending into the pile foundation cavity 103 located inside the large dissolution cavity protective wall 106 is the second portion;

[0065] The first portion is fixedly connected to the steel cage 105 , and the second portion is not fixedly connected to the steel cage 105 .

[0066] In this embodiment, when the outer wall of one portion of the large cavity retaining wall 106 is damaged by poured concrete, the portion of the array displacement meter 302 and flexible inclinometer tube 301 located at the second position farthest from the damaged portion of the large cavity retaining wall 106 moves in the direction of concrete flow, while the portion located at the first position remains fixed to the steel cage 105 and does not move in the direction of concrete flow. The array displacement meter 302 and flexible inclinometer tube 301 of the present invention can be fixedly connected to the steel cage 105 at locations where lateral displacement measurement is not required, while locations where lateral displacement measurement is required are not fixedly connected to the steel cage 105. This allows monitoring of damage to the large cavity retaining wall 106 while maintaining the array displacement meter 302 and flexible inclinometer tube 301 in place, resulting in an ingenious structural design.

[0067] See also Figure 2 、 Figure 5 and Figure 6 , the pressure measuring unit also includes a protective tube 203 and a fixing bracket 204;

[0068] The pressure sensor 201 is installed in the protective tube 203, and the pressure measuring surface 206 of the pressure sensor 201 is close to the inner wall of the large cavity protective wall 106 to measure the lateral pressure of the inner wall of the large cavity protective wall 106 in the pile foundation;

[0069] One end of the fixing bracket 204 is fixedly mounted on the protective tube 203 , and the other end of the fixing bracket 204 includes a plurality of fixing ends 205 , and the plurality of fixing ends 205 are all fixedly connected to the steel cage 105 ;

[0070] The manner in which the fixed end 205 of the fixing bracket 204 is fixedly connected to the steel cage 105 is not limited here, and it can be welded to the steel cage 105 or tied to the steel cage 105 by steel bars.

[0071] In this embodiment, when securing pressure sensor 201 to rebar cage 105, pressure sensor 201 is first installed within protective tube 203. Then, fixed end 205 of fixing bracket 204 is secured to rebar cage 105, thereby securing pressure sensor 201 to rebar cage 105 and awaiting subsequent operations. Pressure sensor 201 of the present invention is secured to rebar cage 105 via multiple fixed ends 205 of fixing bracket 204, thereby enhancing the stability of pressure sensor 201 when monitoring lateral pressure.

[0072] See also Figure 5 , the pressure sensor 201 is located outside the steel cage 105 .

[0073] In this embodiment, after the steel cage 105 with the pressure sensor 201 installed is fixedly inserted into the pile foundation cavity 103, the pressure measuring surface 206 of the pressure sensor 201 is close to the inner wall of the large cavity protective wall 106, and the pressure sensor 201 is located outside the steel cage 105. After concrete is poured into the pile foundation cavity 103, the pressure sensor 201 monitors the lateral pressure of the concrete on the inner wall of the large cavity protective wall 106. The pressure measuring surface 206 of the pressure sensor 201 of the present invention is set close to the inner wall of the large cavity protective wall 106, and the pressure sensor 201 is located outside the steel cage 105 to be close to the inner wall of the large cavity protective wall 106, thereby ensuring the accuracy of the data measured by the pressure sensor 201 on the lateral pressure of the concrete on the inner wall of the large cavity protective wall 106.

[0074] See also Figures 1 to 7 The present invention also provides a large-cavity pile foundation retaining wall stability monitoring test method, including the large-cavity pile foundation retaining wall stability monitoring test device described above, the test method comprising:

[0075] Preparation steps: prepare a geotechnical model trench 101 filled with foundation filling material 102, bury a box body 104 in the foundation filling material 102, and use a pile driver to drill a pile foundation cavity 103 in the foundation filling material 102 so that the pile foundation cavity 103 passes through the box body 104 from top to bottom and communicates with the interior of the box body 104;

[0076] In the preparation step, the foundation formed by the foundation filling material 102 is a foundation simulating a construction site;

[0077] Large cavity backfilling step: the large cavity filler is poured into the box body 104 through the pile foundation cavity 103, and the large cavity filler is repeatedly drilled by the drilling rig to fill the large cavity filler into the box body 104, thereby forming a large cavity protective wall 106;

[0078] In the large cavity backfilling step, the large cavity filling material is a mixture of stone flakes, clay, cement, etc.;

[0079] Installation steps: Install the pressure sensor 201, the flexible inclinometer tube 301 and the array displacement meter 302 on the steel cage 105;

[0080] In the installation step, the pressure sensor 201 is an earth pressure cell;

[0081] Lowering the steel cage 105: inserting the steel cage 105 into the pile foundation cavity 103 and fixing it;

[0082] Pouring step: pouring concrete into the pile foundation cavity 103;

[0083] Monitoring steps: monitor the lateral pressure of the concrete on the inner wall of the large cavity protective wall 106 through the pressure sensor 201, and determine whether the large cavity protective wall 106 is damaged by detecting whether the array displacement meter 302 generates lateral displacement.

[0084] See also Figure 5 In the installation step, the pressure sensor 201 , the flexible inclinometer tube 301 and the array displacement meter 302 are all arranged in a circular array along the axial direction of the steel cage 105 .

[0085] In this embodiment, pressure sensors 201, flexible inclinometer tubes 301, and array displacement meters 302 are installed on the steel cage 105 to be inserted into the pile foundation cavity 103, so that the pressure sensors 201, flexible inclinometer tubes 301, and array displacement meters 302 are arranged in a circular array along the axial direction of the steel cage 105. In the present invention, since the pressure sensors 201, flexible inclinometer tubes 301, and array displacement meters 302 are all arranged in a circular array along the axial direction of the steel cage 105, the pressure sensors 201, flexible inclinometer tubes 301, and array displacement meters 302 are evenly distributed within the large cavity retaining wall 106, thereby enabling monitoring of the pressure on the inner wall and damage to the outer wall of each large cavity retaining wall 106.

[0086] See also Figure 3 In the monitoring step, the pressure sensor 201 measures the change of the lateral pressure of the concrete on the large cavity protective wall 106 to reflect the stress condition of the inner wall of the large cavity protective wall 106.

[0087] In this embodiment, after pouring concrete into the pile foundation cavity 103, after the pressure sensor 201 feeds back the change in the lateral pressure of the concrete on the large cavity protective wall 106 to the pressure data collector 202, the pressure data collector 202 will process the data fed back by the pressure sensor 201 at each time point and output the result. At the same time, it observes the liquid level of the concrete in the pile foundation cavity 103 at each time point, thereby obtaining the relationship between the pressure quantitatively detected by the pressure data collector 202 at each time point and the liquid level of the concrete in the pile foundation cavity 103, so as to simulate how much concrete will be lost during the actual construction process. When recording the pressure data monitored by the pressure sensor 201 at each time point, the present invention correspondingly observes and records the liquid level of concrete in the pile foundation cavity 103 at each time point, thereby obtaining the relationship between the pressure data monitored by the pressure sensor 201 at each time point collected by the pressure data collector 202 and the liquid level of concrete in the pile foundation cavity 103, so as to simulate the amount of concrete loss during the actual construction process, so that the amount of concrete to be used can be prepared during the actual construction process, and concrete can be replenished in time when the concrete liquid level in the pile foundation cavity 103 drops.

[0088] See also Figure 2 、 Figure 4 and Figure 7 In the monitoring step, when the large cavity protective wall 106 is destroyed by concrete, the array displacement meter 302 generates lateral displacement along the flow direction of the concrete.

[0089] In this embodiment, after pouring concrete into the pile foundation cavity 103, if the displacement data collector 303 detects lateral displacement of the array displacement meter 302, this indicates damage to the outer wall of the large cavity retaining wall 106 at the location farthest from the array displacement meter 302. The present invention determines whether damage to the outer wall of the large cavity retaining wall 106 at the location farthest from the array displacement meter 302 occurs based on whether lateral displacement of the array displacement meter 302 occurs, as detected by the displacement data collector 303. The simulation is then repeated multiple times by varying the material composition or thickness of the large cavity retaining wall 106, until the outer wall of the large cavity retaining wall 106 is intact (i.e., the array displacement meter 302 does not experience lateral displacement). This allows the simulation to determine the critical value at which damage to the outer wall of the large cavity retaining wall 106 is achieved, allowing for practical use in construction.

[0090] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A large-cavity pile foundation wall stability monitoring test device, characterized in that: The test device comprises: A geotechnical model trough, a large dissolution cavity filler, a pile foundation cavity and a box body, wherein the geotechnical model trough is filled with the foundation filler, the box body is buried in the foundation filler, the large dissolution cavity filler is filled into the box body to form a large dissolution cavity protective wall, the volume of the large dissolution cavity protective wall is smaller than the volume of the box body, and the pile foundation cavity extends into the large dissolution cavity protective wall after the foundation filler penetrates the box body; A steel cage is fixedly inserted into the pile foundation cavity, wherein the axial direction of the steel cage is consistent with the axial direction of the pile foundation cavity; A plurality of pressure measuring units, wherein the plurality of pressure measuring units are arranged in a circular array along the axial direction of the steel cage, the pressure measuring units including pressure sensors, the pressure sensors being fixedly connected to the steel cage, the pressure sensors being located within the large dissolution cavity retaining wall, and when concrete is poured within the pile foundation cavity, the pressure sensors monitor the pressure of the concrete within the large dissolution cavity retaining wall to reflect the lateral pressure of the inner wall of the large dissolution cavity retaining wall; A displacement measuring unit, comprising a plurality of displacement measuring assemblies, each of which is fixedly connected to the steel cage. The plurality of displacement measuring assemblies are arranged in a circular array along the axial direction of the steel cage. When the outer wall of the large cavity protective wall is damaged by the pouring of concrete, the displacement measuring assemblies generate lateral displacement along with the flow of concrete to reflect whether the outer wall of the large cavity protective wall is damaged; The displacement measurement assembly includes a flexible inclinometer tube and an array displacement meter; The flexible inclinometer tube is fixed on the steel cage, the axial direction of the flexible inclinometer tube is parallel to the axial direction of the steel cage, and the array displacement meter is fixedly installed in the flexible inclinometer tube; When the outer wall of the large cavity protective wall is destroyed by concrete, the array displacement meter generates lateral displacement along the flow direction of the concrete; The portion of the flexible inclinometer tube extending into the pile foundation cavity above the large dissolution cavity protective wall is the first portion, and the portion of the flexible inclinometer tube extending into the pile foundation cavity inside the large dissolution cavity protective wall is the second portion; The first portion is fixedly connected to the steel cage, and the second portion is not fixedly connected to the steel cage.

2. A large-cavity pile foundation wall stability monitoring test device according to claim 1, characterized in that: The flexible inclinometer tube and the array displacement meter are both located inside the steel cage.

3. A large-cavity pile foundation wall stability monitoring test device according to claim 1, characterized in that: The pressure measuring unit also includes a protective tube and a fixing bracket; The pressure sensor is installed in the protective tube, and the pressure measuring surface of the pressure sensor is close to the inner wall of the large dissolution cavity protective wall to measure the lateral pressure of the inner wall of the large dissolution cavity protective wall in the pile foundation; One end of the fixing bracket is fixedly mounted on the protection tube, and the other end of the fixing bracket includes a plurality of fixing ends, and the plurality of fixing ends are all fixedly connected to the steel cage.

4. A large-cavity pile foundation wall stability monitoring test device according to claim 1, characterized in that: The pressure sensor is located outside the steel cage.

5. A large-cavity pile foundation retaining wall stability monitoring test method, comprising a large-cavity pile foundation retaining wall stability monitoring test device according to any one of claims 1 to 4, characterized in that: The test method includes: Preparation steps: prepare a geotechnical model trench filled with foundation filling, bury a box in the foundation filling, and drill a pile foundation cavity in the foundation filling so that the pile foundation cavity passes through the box from top to bottom and communicates with the interior of the box; Large cavity backfilling step: put the large cavity filler into the box through the pile foundation cavity, and repeatedly drill the large cavity filler into the box through the drilling rig to form a large cavity protective wall; Installation steps: Install the pressure sensor, flexible inclinometer tube and array displacement meter on the steel cage; Steps for lowering the steel cage: insert the steel cage into the pile foundation cavity and fix it; Pouring step: pouring concrete into the pile foundation cavity; Monitoring steps: monitor the lateral pressure of concrete on the inner wall of the large cavity retaining wall through a pressure sensor, and determine whether the large cavity retaining wall is damaged by observing whether the array displacement meter produces lateral displacement.

6. A large cavity pile foundation retaining wall stability monitoring test method according to claim 5, characterized in that: In the installation step, the pressure sensor, the flexible inclinometer tube and the array displacement meter are all arranged in a circular array along the axial direction of the steel cage.

7. A large cavity pile foundation retaining wall stability monitoring test method according to claim 5, characterized in that: In the monitoring step, the pressure sensor measures the change of the lateral pressure of the concrete on the large cavity retaining wall to reflect the stress condition of the inner wall of the large cavity retaining wall.

8. A large cavity pile foundation retaining wall stability monitoring test method according to claim 5, characterized in that: In the monitoring step, when the large cavity protective wall is destroyed by concrete, the array displacement meter generates lateral displacement along the flow direction of the concrete.

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